Recently various industries, such as the paper-making industry, are using wood chips produced from entire tree processing, as distinguished from those produced only from debarked logs. This has been possible since 1970 when the machine disclosed in U.S. Pat. No. 3,661,333 was introduced to reduce an entire tree with attached limbs and branches to chips. The tree reduction machine described in the patent, which can be used in the forest near the tree felling site, produces a chip mixture which includes pieces of relatively small branches and twigs which are not in chip form, cards, and pieces of bark which may be referred to as overs, bark and leaf dust, and small chip pieces which may be referred to as fines, and chips, some with adhering bark, of a substantially uniform size which are useful in the paper-making and other industries. The overs may be fed to a rechipper while the fines are used in the energy industry as a low cost fuel. Quite normally, the trees being processed are those not suited to the production of lumber which have been "thinned" from existing forest stands to permit the remaining trees to have unimpeded further growth. Alternatively, with trees which do contain usable lumber in their lower extremities, bucking lengths may be severed prior to the chipping operation. Previous efforts to resolve the problems involved with separating the wood chips from the remainder of the material have included the use of vibratory screen apparatus of the type disclosed in our co-pending application Ser. No. 236,032, filed Feb. 19, 1981, now U.S. Pat. No. 4,351,719.
The present system, as disclosed in U.S. Pat. No. 4,396,501 and the present application, represents another approach to the separation which is required which involves the augering of the chips across stationary, curvilinear, perforate surfaces at a controlled rate to achieve the separating action, as distinguished from the agitating of flat perforate surfaces. The system disclosed herein may be used as a companion machine to the tree reducing machine in the forest or as a processor at a secondary site, and is particularly designed for large volume operations capable, for example, of processing more than one hundred tons of material per hour at a secondary site.
One of the prime objects of the present invention is to design a high-volume system which is extremely effective and efficient in separating the overs and the fines from the useable wood chips.
A still further object of the invention is to provide a system which permits an operator to bypass the overs and useable wood chip augers, and route the products of, for example, tree top chipping, which are for the most part small branches, twigs, and foliage debris, directly to the fines conveyor. The selectable routing system is also useful in the chipping of low quality waste wood of the type which accumulates on the forest floor and is useful as fuel. Material of this character, which always has been left to rot, may now be very efficiently chipped at the time paper quality chips are being produced, and used as fuel.
Another object of the invention is to design a machine of the character described which substantially scrubs off and pulverizes the softer adhering bark, but does not damage the chips - and efficiently processes the material so rapidly that processing costs are relatively minimal and great economies in these operations can be achieved.
Still another object of the invention is to provide a system which deposits the separated material in segregated piles which can be readily removed in a high volume operation, or channels it to separate stations from which it may be delivered directly to transport vehicles.
SUMMARY OF THE INVENTION
Chip material comprising overs, acceptable chips, and fines are supplied via a bin to an auger system which transports them in a metered volume along a first stationary screen trough having openings of a size to pass the acceptable chips and fines while retaining the overs. The acceptable chips and fines passing through the screen are collected and augered along a second, underlying stationary screen trough having openings of a size to pass the fines while retaining the acceptable chips. The overs are collected and reprocessed. The acceptable chips are augered forwardly to a discharge station. The fines which are passed through the second screen trough are collected at a separate station. A routing system may be employed which, under operator control, permits the chipped material to be fed directly to the fines auger.
Other objects of the invention will become apparent with reference to the following specification and to the drawings.